JP2023526739A - High-strength high-temperature corrosion-resistant martensitic stainless steel and method for producing the same - Google Patents

Abstract

The following chemical elements in mass %: 0<C≦0.05%, Si from 0.1% to 0.2%, Mn from 0.20% to 1.0%, Cr from 11.0% 14.0%, Ni 4.0%-6.0%, Mo 1.5%-2.5%, N 0.001%-0.10%, V 0.03%-0. 2%, 0.01% to 0.1% of Nb, 0.01% to 0.04% of Al, and the balance being Fe and unavoidable impurities. A hot corrosive martensitic stainless steel is disclosed. Also disclosed are tubing and casings made from the high-strength, hot-corrosion-resistant martensitic stainless steels described above, and methods of making the tubing and casings. The high-strength, hot-corrosion-resistant martensitic stainless steel of the present disclosure has excellent hot-corrosion resistance to carbon dioxide and chloride ions, and also has excellent low-temperature impact toughness and high-temperature strength deterioration resistance.

Description

TECHNICAL FIELD The present disclosure relates to metallic materials and methods of manufacturing the same, and more particularly to stainless steel and methods of manufacturing the same.

In modern oil and gas production, mining at depths of 6000 m and above and in ultra-deep wells has become a major problem these days. The usage environment of pipes and casings in these deep wells and ultra-deep wells is becoming more and more severe, mainly due to high temperature, high pressure, and highly corrosive environments containing large amounts of CO ₂ , Cl ⁻ and the like. Also, since many oil and gas resources are located in relatively cold regions, temperatures can drop below -20°C during winter operations. Such harsh environments generally require high alloy products, such as super martensitic stainless steels, to meet corrosion resistance. Existing super martensitic stainless steels have excellent corrosion resistance in environments where high concentrations of CO ₂ and Cl ⁻ ions exist at high temperatures. Material strength in the service environment is also necessary to meet safety design requirements for tubing and casing.

Ultra-low carbon martensitic stainless steels traditionally used for tubing and casing mainly contain 12.5% Cr, 5.0% Ni and 2% Mo. This composition can only be used for 110 ksi (kilopounds per square inch) tubing and casing. To obtain higher grades, it is necessary to add high alloying elements such as Cr and expensive Mo elements.

Patent Document 1 entitled "High-strength stainless steel seamless pipe for oil well and manufacturing method thereof" published on July 4, 2017 discloses ferrite , martensite and austenite, and has excellent resistance to carbon dioxide gas corrosion and sulfide stress corrosion cracking, and has a strength of 110 ksi and even up to 125 ksi. This stainless steel pipe contains the following chemical components. That is, C is 0.05% or less, Si is 0.5% or less, Mn is 0.15% to 1.0%, P is 0.030% or less, S is 0.005% or less, and Cr is 15%. 5% to 17.5%, Ni 3.0% to 6.0%, Mo 1.5% to 5.0%, Cu 4.0% or less, W 0.1% to 2.5% %, and N is 0.15% or less. The high-strength stainless steel seamless pipe of the present invention, which has excellent corrosion resistance, has excellent carbon dioxide gas corrosion resistance in a high temperature environment up to 200 ° C. when it contains CO ₂ and Cl ^- , and further contains H ₂ S. Excellent sulfide stress cracking resistance and excellent sulfide stress corrosion cracking resistance in corrosive environments. Comparatively, this composition is very difficult to manufacture due to the difficult texture control and thus its manufacturing cost is too high for oil field use.

"High-strength martensitic stainless steel with excellent carbon dioxide gas corrosion resistance and resistance to sulfide stress corrosion cracking" published on February 1, 2006. and sulfide stress corrosion cracking resistance") describes a high-strength martensitic stainless steel excellent in carbon dioxide corrosion resistance and sulfide stress corrosion cracking resistance and having a yield strength of 860 MPa or more. Discloses a high-strength martensitic stainless steel characterized by This high-strength martensitic stainless steel contains the following chemical components. That is, C 0.005% to 0.04%, Si 0.5% or less, Mn 0.1% to 3.0%, P 0.04% or less, S 0.01% or less, Cr 10% to 15%, Ni 4.0% to 8%, Mo 2.8% to 5.0%, Al 0.001% to 0.10%, N 0.07% or less with the balance being Fe and impurities, satisfying the following formula: Mo≦2.3−0.89Si+32.2C. This high-strength martensitic stainless steel has a metal structure mainly composed of tempered martensite, carbides that precipitate during tempering, and intermetallic compounds (for example, Laves phase or σ phase that precipitates finely during tempering). have. This steel is characterized by high strength, but on the other hand it is also of high cost due to the presence of detrimental intermetallics (eg σ-phase in the precipitation phase) and high Mo content.

It can be seen that the stainless steels disclosed in the prior art are mainly concerned with the corrosion resistance of stainless steel materials, and do not include the performance of strength deterioration of stainless steels at high temperatures.

China Patent No. 104884658B China Patent No. 1729306A

One object of the present disclosure is to provide a high strength, hot corrosion resistant martensitic stainless steel. This high-strength, hot-corrosion-resistant martensitic stainless steel has a yield strength of up to 125 ksi and is suitable for use in environments above 180° C. and containing high concentrations of carbon dioxide (CO ₂ ). It has excellent high-temperature corrosion resistance to ions, excellent low-temperature impact toughness, and high-temperature strength deterioration resistance.

To achieve the above objectives, the present disclosure provides a high-strength, hot-corrosion-resistant martensitic stainless steel containing the following chemical elements in mass %. i.e.
0<C≦0.05%, Si 0.1% to 0.2%, Mn 0.20% to 1.0%, Cr 11.0% to 14.0%, Ni 4.0% % to 6.0%, Mo 1.5% to 2.5%, N 0.001% to 0.10%, V 0.03% to 0.2%, Nb 0.01% to 0.1%, and 0.01% to 0.04% Al.

Preferably, the high-strength, hot-corrosion-resistant martensitic stainless steel according to the present disclosure contains the following chemical elements in mass %. i.e.
0<C≦0.05%, Si 0.1% to 0.2%, Mn 0.20% to 1.0%, Cr 11.0% to 14.0%, Ni 4.0% % to 6.0%, Mo 1.5% to 2.5%, N 0.001% to 0.10%, V 0.03% to 0.2%, Nb 0.01% to 0.1%, 0.01% to 0.04% Al, and the balance is Fe and unavoidable impurities.

The design principle of each chemical element in the high-strength, high-temperature corrosion-resistant martensitic stainless steel according to the present disclosure is as follows.

C (Carbon): In the high-strength, hot-corrosion-resistant martensitic stainless steel according to the present disclosure, carbon is used as an austenite-forming element in the martensitic stainless steel grade. By increasing the C content, the rate of austenitizing stainless steel at high temperature can be increased, and martensite can be obtained at room temperature, which can improve the strength of the steel. However, it should be noted that if the C content in the steel is too high, the corrosion resistance of the stainless steel will be reduced, and at the same time the toughness will also be reduced. Therefore, in the high-strength, hot-corrosion-resistant martensitic stainless steel of the present disclosure, the mass % of C is controlled so that 0<C≦0.05%.

In some preferred embodiments, the mass % of C can be controlled between 0.003% and 0.05% to meet strength requirements while ensuring corrosion resistance.

Si (silicon): In the high-strength, hot-corrosion-resistant martensitic stainless steel according to the present disclosure, Si is an important deoxidizing agent in the steelmaking process. However, Si promotes the formation of σ phase and ferrite phase in stainless steel with high Cr content, and there is a risk that σ phase and ferrite phase adversely affect the toughness and corrosion resistance of the stainless steel. Therefore, in the high-strength, high-temperature corrosion-resistant martensitic stainless steel of the present disclosure, the mass % of Si is controlled to be 0.1% to 0.2%.

Mn (manganese): In the high-strength, high-temperature corrosion-resistant martensitic stainless steel according to the present disclosure, Mn can improve the strength of the stainless steel. In the present disclosure, 0.2% by mass or more of Mn is added to ensure the necessary strength of the pipe material and casing. However, when the mass % of Mn exceeds 1.0%, the toughness of the stainless steel is lowered. Therefore, in the high-strength, high-temperature corrosion-resistant martensitic stainless steel of the present disclosure, the mass % of Mn is controlled to be 0.20% to 1.0%.

In some preferred embodiments, the mass % of Mn can be controlled to be between 0.20% and 0.5% in order to reduce corrosion resistance deterioration due to Mn segregation.

Cr (chromium): In the high-strength, high-temperature corrosion-resistant martensitic stainless steel according to the present disclosure, Cr is an important element for improving the corrosion resistance of the stainless steel. By adding Cr, it is possible to form a corrosion-resistant passive film on the surface of stainless steel quickly in air in time, thereby improving the _CO2 corrosion resistance of pipes and casings in high-temperature environments. can be improved. In the present disclosure, the mass % of Cr added in the high-strength, hot-corrosion-resistant martensitic stainless steel is 11 so that the resulting stainless steel has _CO2 corrosion resistance at 180°C or higher. should reach 0.0% or more. However, if the mass% of the Cr element added to the steel exceeds 14.0%, the risk of ferrite precipitation increases, which adversely affects the hot workability and corrosion resistance of the product. Should. Therefore, in the high-strength, hot-corrosion-resistant martensitic stainless steel of the present disclosure, the mass % of Cr is controlled to be 11.0% to 14.0%.

In some preferred embodiments, the mass % of Cr can be controlled to be between 11.5% and 13.5% for better corrosion resistance.

Ni (nickel): In the high-strength, high-temperature corrosion-resistant martensitic stainless steel according to the present disclosure, Ni is an important element for expanding the austenite region in the stainless steel. Ni can not only improve the corrosion resistance and toughness of stainless steel, but also effectively improve the stress corrosion cracking resistance of stainless steel under high temperature conditions. To obtain this effect, the Ni content in the high-strength, hot-corrosion-resistant martensitic stainless steel of the present disclosure should be greater than 4.0%. However, it should be noted that Ni is also a relatively valuable alloying element. In the high-strength, high-temperature corrosion-resistant martensitic stainless steel, when the Ni mass% exceeds 6%, an austenitic phase whose strength cannot be controlled by heat treatment appears in the structure, thereby increasing the strength of the stainless steel. reduce Therefore, in the high-strength, high-temperature corrosion-resistant martensitic stainless steel of the present disclosure, the Ni mass% is controlled to be 4.0% to 6.0%.

In some preferred embodiments, the mass % of Ni can be controlled to be between 4.5% and 5.5% for better corrosion resistance.

Mo (molybdenum): In the high-strength, high-temperature corrosion-resistant martensitic stainless steel according to the present disclosure, Mo is an element that improves the resistance of the stainless steel to pitting corrosion caused by Cl ions, especially in a high-temperature environment of 150°C or higher. However, it should be noted that Mo is a noble metal element. Also, when the content of Mo in the high-strength, hot-corrosion-resistant martensitic stainless steel according to the present disclosure exceeds 2.5%, a large amount of ferrite is formed, thereby improving the hot workability and resistance of the stainless steel product. adversely affect both corrosiveness. Therefore, in the high-strength, hot-corrosion-resistant martensitic stainless steel according to the present disclosure, the mass % of Mo is controlled to be 1.5% to 2.5%.

In some preferred embodiments, the mass % of Mo can be controlled to be 1.8-2.3% for better corrosion resistance.

N (Nitrogen): In the high-strength, high-temperature corrosion-resistant martensitic stainless steel according to the present disclosure, N is an element that improves the pitting corrosion resistance of the stainless steel. On the other hand, N, as an austenite-forming element, can increase the martensite ratio of the stainless steel according to the present disclosure, thereby effectively improving the strength of the stainless steel. However, if the N element content in the steel is too high, nitrides are likely to be formed and the toughness of the stainless steel is reduced. Therefore, in the high-strength, hot-corrosion-resistant martensitic stainless steel according to the present disclosure, the mass % of N is controlled to be 0.001% to 0.10%.

Al (aluminum): In the high-strength, hot-corrosion-resistant martensitic stainless steel according to the present disclosure, Al is added as a deoxidizing agent during the smelting process. In order to obtain the deoxidizing effect, the amount of Al added should be 0.01% or more. However, if the Al content exceeds 0.04%, the toughness of the stainless steel is lowered. Therefore, in the high-strength, hot-corrosion-resistant martensitic stainless steel according to the present disclosure, the mass % of Al is controlled to be 0.01% to 0.04%.

V, Nb (vanadium, niobium): Both V and Nb are important micro-alloying elements in the high-strength, hot-corrosion-resistant martensitic stainless steel according to the present disclosure. In general, grains can be refined by the pinning effect of precipitation of carbonitrides, thereby improving the strength of stainless steel. However, through detailed research, the present inventors have found in the present disclosure that combined addition of V and Nb can form vanadium niobium carbonitrides. Uniform distribution of the vanadium niobium carbonitride can improve the strength of the stainless steel while refining the crystal grains. In order to obtain the above effect, the added amount of the V element in the stainless steel must be 0.03% or more, and the added amount of the Nb element must be 0.01% or more. However, on the other hand, V and Nb are noble metal elements. increases significantly and the toughness of the stainless steel decreases. Therefore, in the high-strength, high-temperature corrosion-resistant martensitic stainless steel according to the present disclosure, the mass% of V is controlled to be 0.03% to 0.2%, and the mass% of Nb is 0.01%. It is controlled to be ~0.1%.

Preferably, in the high-strength, hot-corrosion-resistant martensitic stainless steel according to the present disclosure, the content of chemical elements in mass % satisfies (V+Nb):(C+N)=2:1 to 8:1. V, Nb, C and N each represent the content of the corresponding element in mass %.

In the above technical solution, in the high-strength, high-temperature corrosion-resistant martensitic stainless steel according to the present disclosure, the content of V, Nb, C and N in mass% (V + Nb): (C + N) = 2: 1 ~ By controlling the ratio to satisfy 8:1, the effect of improving and increasing the strength and toughness of stainless steel by the above elements can be effectively realized.

Preferably, the high-strength, hot-corrosion-resistant martensitic stainless steel according to the present disclosure further includes at least one of Ti, Zr, and Re, and the content of any one of Ti, Zr, and Re is 0.2% or less, and Ti+Zr+Re≦0.3%. In the formula, Ti, Zr and Re each represent the content of the corresponding element in mass %.

In the technical solution of the present disclosure, the high-strength, high-temperature corrosion-resistant martensitic stainless steel of the present disclosure further includes at least one of Ti, Zr and Re, and Re may be replaced by other rare earth elements . Including one or more of Ti, Zr and Re in stainless steel contributes to the precipitation of carbonitrides and refinement of crystal grains in the stainless steel, thereby improving the strength and toughness of the stainless steel. can be done. However, it should be noted that when the content in mass % of any of these elements exceeds 0.2%, the toughness of the stainless steel is reduced. Therefore, in the high-strength, hot-corrosion-resistant martensitic stainless steel according to the present disclosure, the content of any one of Ti, Zr, and Re is 0.2% or less, and Ti + Zr + Re ≤ 0.3 %.

Preferably, in the high-strength, hot-corrosion-resistant martensitic stainless steel according to the present disclosure, the unavoidable impurity elements include at least S, P, and O, and the content of P, S, and O is, in mass%, P At least one of ≦0.03%, S≦0.01%, and O≦0.004% is satisfied.

P (Phosphorus): In the high-strength, high-temperature corrosion-resistant martensitic stainless steel according to the present disclosure, P is a harmful element that reduces the high-temperature _CO2 corrosion resistance of stainless steel, and improves the hot workability of stainless steel. adversely affect If the P content exceeds 0.03%, the corrosion resistance of stainless steel does not meet the required performance in a high temperature environment. Therefore, in the high-strength, hot-corrosion-resistant martensitic stainless steel according to the present disclosure, the content of P in mass% is controlled so that P≦0.03%.

In some preferred embodiments, the weight percent of P can be controlled such that P≦0.015% in order to obtain better corrosion resistance.

S (sulfur): In the high-strength, hot-corrosion-resistant martensitic stainless steel according to the present disclosure, S is a harmful element that reduces the hot workability of the stainless steel and adversely affects the impact toughness of the stainless steel. If the mass % of S exceeds 0.01%, the steel pipe cannot be produced normally. Therefore, in the high-strength, hot-corrosion-resistant martensitic stainless steel according to the present disclosure, the S content (% by mass) is controlled so that S≦0.01%.

In some preferred embodiments, the weight percent of S can be controlled such that S≦0.005% in order to obtain better corrosion resistance.

O (oxygen): In the high-strength, hot-corrosion-resistant martensitic stainless steel according to the present disclosure, the O element exists as an oxide in the steel, which adversely affects the hot workability, impact toughness, and corrosion resistance of the stainless steel. give. Therefore, in the high-strength, hot-corrosion-resistant martensitic stainless steel according to the present disclosure, the O content is controlled so that O≦0.004% by mass.

Preferably, in the high-strength, hot-corrosion-resistant martensitic stainless steel according to the present disclosure, in order to obtain high strength and hot-corrosion resistance, the content of chemical elements in mass % satisfies at least one of the following: i.e.
0.003% to 0.05% of C,
Mn from 0.20% to 0.5%,
11.5% to 13.5% Cr,
4.5% to 5.5% Ni and
Mo from 1.8% to 2.3%.

Preferably, the high strength hot corrosion resistant martensitic stainless steel according to the present disclosure has at least one of the following properties. yield strength at 180°C greater than or equal to 800 MPa; impact energy at -20°C greater than or equal to 140 J; ₂ and a uniform corrosion rate of 0.125 mm/a or less in an environment containing high Cl ⁻ concentration. An environment comprising _CO2 is, for example, a partial pressure of _CO2 of 2 MPa or more, for example 6 MPa. An environment containing a high Cl ⁻ concentration is, for example, a chloride ion concentration of 50000 mg/L or higher, for example a chloride ion concentration of 100000 mg/L.

Accordingly, another object of the present disclosure is to provide tubing and casings having a yield strength of up to 125 ksi. This pipe material and casing are suitable for use in a high-concentration environment where the temperature is 180° C. or higher and the partial pressure of carbon dioxide (CO ₂ ) is 2 MPa or higher, and has excellent high-temperature corrosion resistance to carbon dioxide and chloride ions. It has excellent low-temperature impact toughness, high yield strength even above 180° C., ie resistance to strength deterioration at high temperatures, and has the important advantages of high strength, high toughness and high corrosion resistance.

To achieve the above objectives, the present disclosure provides tubing and casings made from high strength, hot corrosion resistant martensitic stainless steel as described above.

It is therefore a further object of the present disclosure to provide a method of manufacturing tubing and casings as described above. The pipe material and casing obtained by this manufacturing method have a yield strength of up to 125 ksi, are suitable for use in an environment of 180 ° C. or higher and high concentrations of carbon dioxide (CO ₂ ), and have excellent resistance to carbon dioxide and chloride ions. It has excellent high temperature corrosion resistance, excellent low temperature impact toughness and high temperature strength deterioration resistance, and has the important advantages of high strength, high toughness and high corrosion resistance.

In order to achieve the above objectives, the present disclosure provides a method of manufacturing tubing and casing as described above, which method includes the following steps. i.e.
(1) manufacturing a pipe blank;
(2) manufacturing a seamless pipe from the pipe blank and then cooling the seamless pipe to room temperature;
(3) Quenching: The seamless tube is heated to a temperature of _AC 3-1050° C. and heat preserved for t×(0.5-3) minutes; C./s cooling rate to temperature T1, and thermal storage is performed for t×(0.5-1.5) minutes, T1=M _S −80° C., M _S at the start of martensite transformation. a step that is temperature;
(4) First tempering: The seamless tube is heated to temperature T2 for tempering treatment, thermal storage is performed for t×(3-7) minutes, and then the seamless tube is heated from 5° C./s to 30° C./ cooling to 100° C. or less at a cooling rate of 1 sec and T2 in the range of 500° C. to A _C 3;
(5) Second tempering: The seamless tube is heated to temperature T3 for the second tempering treatment, and heat preservation is performed for t×(3-7) minutes, and then the seamless tube is heated at 5° C./s. cooling to 100° C. or less at a cooling rate of ˜30° C./sec, where T3=T2−40° C.;
t represents the wall thickness (mm) and A _C 3 is the temperature at which the austenite transformation of the steel ends.

In the method of manufacturing pipes and casings according to the present disclosure, in step (1), pipe blanks are cast by conventional smelting methods, such as continuous casting, ingot casting, using a converter, electric furnace, vacuum induction furnace, etc. etc. can be manufactured. In the step (2), in the process of producing a seamless pipe from the pipe blank, the pipe blank is rolled into a seamless steel pipe of a specified size using a commonly used Mannesmann pipe mill, and then produced. Cool the seamless steel pipe to room temperature.

The reason for controlling the heating temperature of the seamless tube to A _C 3 to 1050° C. in step (3) is that if the heating is performed at a temperature lower than A _C 3, the stainless steel of the present disclosure cannot be sufficiently austenitized, This makes it difficult to obtain uniform precipitation on the stainless steel in subsequent treatments. In some preferred embodiments, heating is preferably performed at a temperature of 1000° C. or less. If the quenching heating temperature exceeds 1000° C., an austenitic structure grows, thereby deteriorating the impact toughness of the stainless steel. Furthermore, in step (3), after the stainless steel is fully austenitized and heat-preserved, the heat-preservation process is performed at temperature T1 during the cooling process, so that the carbides of V and Nb are retained between the martensite laths. At the same time, the reduction of C content in the martensite lath can effectively improve the toughness and plasticity of the martensite matrix. In the subsequent heat preservation process at tempering temperature T2 in step (4), reverse transformed austenite is formed between the martensitic laths and carbides of V and Nb migrate into the reverse transformed austenite, thereby increasing the strength of the stainless steel. Improve strength. The metallographic structure is reverse transformed austenite and retained austenite formed between the martensitic lath base and part of the lath boundary. Next, in step (5) in the above solution, the second tempering treatment transforms the martensite that was not decomposed in the first tempering to form new reverse transformed austenite, thereby improving room temperature strength and low temperature impact Toughness and strength above 180° C. can be improved while decreasing the hardness of stainless steel.

Compared to the conventional ultra-low carbon martensitic stainless steel without combined addition of Nb and V, and the quenching and tempering process, the technical solution of the present disclosure can greatly improve strength, toughness and plasticity. can. In addition, since the distribution of carbides becomes more uniform, the structure after tempering becomes finer, thereby improving the strength and corrosion resistance in long-term use at a high temperature of 180°C.

Preferably, in the method for manufacturing tubing and casing according to the present disclosure, in step (3), the heating temperature is A _C 3-1000°C.

Compared with the prior art, the high-strength, hot-corrosion-resistant martensitic stainless steel and its production method have the following advantages and beneficial effects.

With rational chemical composition system design, the present disclosure provides high strength hot corrosion resistant martensitic stainless steel, which has a yield strength of up to 125 ksi and a high concentration of carbon dioxide at 180°C or higher. It is suitable for use in a (CO ₂ ) environment, has excellent high-temperature corrosion resistance to carbon dioxide and chloride ions, and has excellent low-temperature impact toughness and high-temperature strength deterioration resistance.

Tubing and casings made from the high-strength, hot-corrosion-resistant martensitic stainless steel of the present disclosure also have excellent properties with the major advantages of high strength, high toughness, and high corrosion resistance, and are It can be used effectively in harsh environments.

The high-strength, hot-corrosion-resistant martensitic stainless steel and its production method according to the present disclosure are further described and illustrated below with respect to specific examples, which unduly limit the technical solutions of the present invention. isn't it.

Examples 1-15 and Comparative Examples 1-7
Table 1 shows mass % of chemical elements contained in the high-strength, high-temperature corrosion-resistant martensitic stainless steels of Examples 1-15 and the stainless steels of Comparative Examples 1-7.

The tubes made from the high-strength, hot-corrosion-resistant martensitic stainless steel of Examples 1-15 and the tubes made from the stainless steel of Comparative Examples 1-3 were made by the following steps.
(1) A pipe blank was manufactured.
(2) A seamless pipe having an outer diameter of 88.9 mm and a wall thickness of 7.34 mm was produced from the pipe blank and then cooled to room temperature.
(3) Quenching: The seamless tube is heated to a temperature of A _C 3 to 1050° C., preferably A _C 3 to 1000° C., and heat stored for t × (0.5 to 3) minutes (shown as the first heat storage time ). After that, the seamless tube was cooled to temperature T1 at a cooling rate of 2° C./sec to 40° C./sec and heat-stored for t×(0.5-1.5) minutes (indicated as the second heat storage time). . T1=M _S −80° C., M _S is the temperature at the start of martensite transformation.
(4) First tempering: The seamless tube is heated again to temperature T2 for tempering treatment, heat-storage for t×(3-7) minutes (indicated as the third heat-storage time), and then 5° C./sec. Cooled to 100° C. or less at a cooling rate of ˜30° C./sec. The range of T2 is from 500° C. to A _C 3.
(5) Second tempering: The second tempering treatment is performed at temperature T3, heat stored for t×(3 to 7) minutes (shown as the fourth heat storage time), and then heated at a temperature of 5° C./sec to 30° C./sec. It cooled to 100 degrees C or less at the cooling rate. T3=T2-40° C., and t represents the thickness (mm).

Referring to Table 1, note that the stainless steel grades of Comparative Examples 4-6 correspond to the grades of Comparative Examples 1-3, B1-B3, respectively. For the stainless steel tubes of Comparative Examples 4-6, only conventional heat treatment methods were used. That is, the seamless tube was heated at 1000° C. for 30 minutes, air-cooled to room temperature, then tempered once at 600° C., and heat-stored for 40 minutes.

Tables 2-1 and 2-2 show specific process parameters in each step of the manufacturing methods of Examples 1-15 and Comparative Examples 1-3.

The relevant properties, such as yield strength YS, tensile strength TS, impact toughness, etc., of the tubes made from the high strength hot corrosion resistant martensitic stainless steels of Examples 1-15 and the stainless steels of Comparative Examples 1-7 were tested. and obtained test data to evaluate each of their properties. The specific test items and test methods are as follows.
1) Yield strength and tensile strength test: The produced steel pipe was processed into API arc test pieces, and yield strength test data was obtained by taking the average value based on the ISO6892 standard after the test.
2) High-temperature yield strength test: The produced steel pipe was processed into a near-arc test piece, and a high-temperature tensile test was performed based on the ISO6892 standard, and the yield strength was determined by taking the average value.
3) Charpy V-notch impact absorption energy (i.e., impact toughness) test: A V-notch impact test piece with a volume of 5 x 10 x 55 (mm) is taken from a steel pipe, and the average value after the test is taken based on the GB/T229 standard. , converted to the average value of the full size of 10×10×55 (mm) based on the API5CT standard. The test temperature is -20°C.
4) Corrosion test at high temperature in the presence of CO ₂ and Cl ^- : The test piece was placed in a liquid in an autoclave at a temperature of 180 ° C. with a CO ₂ partial pressure of 6 MPa, a Cl ^- concentration of 100,000 mg / L, and a liquid flow rate of 1 m / s. soaked. The test time was 240 hours. A uniform corrosion rate was calculated by comparing the weight of the specimen before and after the test.

Table 3 lists relevant performance parameters for tubing made from Examples 1-15 and Comparative Examples 1-7.

As can be seen from Table 3, in Examples 1-15 of the present disclosure, the yield strength YS that meets the requirement of 125 ksi is 862 MPa or more, the yield strength at 180° C. is 810 MPa or more, and the impact toughness at −20° C. is 143 J or more, and the uniform corrosion rate at 180° C. in an environment containing CO ₂ and high Cl ⁻ concentration is 0.115 mm/a or less. It can be seen that Examples 1-15 of the present disclosure have the advantage of better overall performance compared to Comparative Examples 1-3 and Comparative Examples 4-6. The components in Comparative Examples 1 to 3 are outside the scope of the disclosure, and the content of Cr element in Comparative Example 1, the content of Mo element in Comparative Example 2, and the content of Ni element in Comparative Example 3 are outside the scope of disclosure. is. Also, (V+Nb):(C+N) was outside the range of 2:1 to 8:1, which resulted in an average corrosion rate of 0.125 mm/a or more and low toughness. In Comparative Examples 4 to 6, in addition to the components being outside the scope of the present disclosure, the quenching method and tempering method were outside the scope of the manufacturing method of the present disclosure, the toughness was further reduced, and the yield strength at high temperatures was low. getting low. Therefore, compared to the comparative examples, the pipe materials manufactured according to Examples 1 to 15 of the present disclosure have excellent hot corrosion resistance to carbon dioxide and chloride ions, and also have excellent low temperature impact toughness and high temperature strength deterioration resistance. It has the great advantage of being highly durable.

It should be noted that the above-described embodiments merely illustrate specific embodiments of the present invention. It is clear that many similar variations or modifications are possible without the invention being limited to the examples described above. Any variation or modification that can be directly derived or easily conceived by a person skilled in the art from the content disclosed in the present disclosure is intended to fall within the protection scope of the present invention.

Claims (10)

The following chemical elements in mass %, i.e.
0<C≦0.05%, Si 0.1% to 0.2%, Mn 0.20% to 1.0%, Cr 11.0% to 14.0%, Ni 4.0% % to 6.0%, Mo 1.5% to 2.5%, N 0.001% to 0.10%, V 0.03% to 0.2%, Nb 0.01% to High-strength, high-temperature corrosion-resistant martensitic stainless steel containing 0.1% Al and 0.01% to 0.04% Al. The following chemical elements in mass %,
0<C≦0.05%, Si 0.1% to 0.2%, Mn 0.20% to 1.0%, Cr 11.0% to 14.0%, Ni 4.0% % to 6.0%, Mo 1.5% to 2.5%, N 0.001% to 0.10%, V 0.03% to 0.2%, Nb 0.01% to 2. The high-strength, hot-corrosion-resistant martensitic stainless steel according to claim 1, containing 0.1% Al, 0.01% to 0.04% Al, and the balance being Fe and unavoidable impurities. 3. The high-strength, hot-corrosion-resistant martensitic stainless steel according to claim 1, wherein the content of said chemical elements in mass % satisfies (V+Nb):(C+N)=2:1 to 8:1. Furthermore, at least one of Ti, Zr and Re is included, and the content of any one of Ti, Zr and Re is 0.2% or less and Ti + Zr + Re ≤ 0.3% The high-strength, hot-corrosion-resistant martensitic stainless steel according to claim 1 or 2. The unavoidable impurity element contains at least S, P and O, and the content of P, S and O in mass% is P ≤ 0.03%, S ≤ 0.01%, and O ≤ 0.004% The high-strength, hot-corrosion-resistant martensitic stainless steel according to claim 2, which satisfies at least one of: The content in mass % of the chemical element is
0.003% to 0.05% of C
0.20% to 0.5% of Mn
11.5% to 13.5% Cr
4.5% to 5.5% Ni and 1.8% to 2.3% Mo;
The high-strength, hot-corrosion-resistant martensitic stainless steel according to claim 1 or 2, which satisfies at least one of: The following properties: yield strength at room temperature of 862 MPa or more, yield strength at 180°C of 800 MPa or more, impact energy at -20°C of 140 J or more, environment containing _CO2 and high ^Cl- concentration at 180°C The high-strength, hot-corrosion-resistant martensitic stainless steel according to claim 1 or 2, having at least one uniform corrosion rate at 0.125 mm/a. Pipes and casings made from the high-strength, hot-corrosion-resistant martensitic stainless steel according to any one of claims 1 to 7. The following steps i.e.
(1) manufacturing a pipe blank;
(2) manufacturing a seamless pipe from the pipe blank and then cooling the seamless pipe to room temperature;
(3) Quenching: The seamless tube is heated to a temperature of _AC 3-1050° C. and heat preserved for t×(0.5-3) minutes; C./sec cooling rate to temperature T1, thermal storage is performed for t×(0.5 to 1.5) minutes, T1=M _S −80° C., M _S is the temperature at the start of martensitic transformation. a step and
(4) First tempering: The seamless tube is heated to temperature T2 for tempering treatment, thermal storage is performed for t×(3-7) minutes, and then the seamless tube is heated from 5° C./s to 30° C./ cooling to 100° C. or less at a cooling rate of 1 sec and T2 in the range of 500° C. to A _C 3;
(5) Second tempering: The seamless tube is heated to temperature T3 for the second tempering treatment, and heat preservation is performed for t×(3-7) minutes, and then the seamless tube is heated at 5° C./s. cooling to 100° C. or less at a cooling rate of ˜30° C./sec, where T3=T2−40° C.;
9. A method for manufacturing tubing and casings according to claim 8, wherein t represents wall thickness (mm). The method for manufacturing tubing and casing according to claim 9, wherein in step (3), the seamless tube is heated to a temperature of A _C 3-1000°C.